sixteen inch disc sander I intend to make?

I used to own a sixteen inch disc belt sander and swapped it to a a guy for a compressor ( turned out to be a bad move he sold it on ebay a few weeks later for sixteen hundred pounds.Anyway I have now bought a twelve inch disc sander with an undercarriage base cabinet to house a dust extractor vacuum machine which is designed to cut the vacuum of a few minutes after switching it off from the front.
It really is very dust efficient.I now have a largeish selection of sixteen inch sandpaper discs which the other guy bought some off me a very few but not all I had.
Anyway I intend to make myself a nice professional sixteen inch disc sander from scratch using a nice powerful motor of which I have several to choose from
. I have a nice big sheet of aluminium treadplate approx quarter inch thick which is a lot more than I need which I intend to use back to front i.e smooth side facing forward . I am thinking of using this for the faceplate which is what I would like my pals here to help me come to a decision hence this post .
First of I could cut the aluminium sheet to a square. I need to find out and would be the easiest way to make it perfectly round.
I figure I could cut it roughly with my bandsaw almost to shape perhaps a shade over sixteen inches and since my metal lathe will not cut sixteen inches, (it is max ten inches ) anyway after a bit of headscratching I considered fitting it through a centre hole which I would need to drill anyway ,and fixing it perhaps to a chuck on my larger woodlathe and try to cut it from the toolpost with a high speed steel parting tool woodturning type taking things easy of course it does work on metal metal I have done it before. I could also set up a wooden jig as did Norm abram many times on t v to do it more carefully on the bandsaw or even on my milling machine.This is done by setting a piece of wood onto the machines table and clamp it tightly to the table then setting a dowel eight inches from the cutting blade or cutter The disc is set onto the dowl tight-ish fit and slowly revolved untill a perfect circle has been achieved. I can do the rest of the machine myself just need advice on the disc really .I could buy a steel disc for around twenty five pounds but am to mean . I would rather use what I have in the way of materials.I could also make the disc much easier with mdf or plywood what do you guys suggest or do you know a british seller of a disc dedicated for a sanding machine??? Alistair

Those little diamond tread patterns will possibly get in the way of your mounting.Aluminum is gummy and will tend to grab your cutting tool. Be careful if you turn with a hand held tool.

I have once turned an almost perfect disk by simply mounting a rough approximate disk on a bolt held in a big heavy vise and captured between two washers, loosely so it could spin. I then used an angle grinder held very lightly against the edge and at a slight angle so the spinning grinder caused the disk to spin.

Having said all this, if I could buy a steel disk, already round and with the center hole drilled for less than $75, that’s the way I’d go. . preferring the weight of the steel.

The edge speed increase from a 10” to a 16” is a huge step. Also the cost of sanding discs is something to consider, as is the ease of swapping grits, when I had my 16” I regretted my purchase from day one, my progression was almost like the “bigger boat syndrome” I now have stepped back from a 10” which I sold. I now have a 8” which I am almost happy with

I don’t believe 1/4” aluminum will be thick enough without reinforcement, it will vibrate around the edges. Also you may have to true the face unless your drivetrain is perfect and the plate dead flat which it probably isn’t.